There are three types of haptics: capacitive, resistive, and piezoelectric. Capacitive touch systems, although they have been known to engineers for years, have only recently become a viable alternative to mechanical switches used in consumer electronics. The main reason was the progress in the technology of programmable integrated circuits combining in one piece analog and digital circuits. Typical capacitive touch systems can be switched by a finger approaching them at a distance of less than 3 mm. However, for larger distances, for example, when it is desirable for a switch to be placed behind thick glasses, the detection of the actual approximation of the finger becomes problematic.
The operation of the capacitive circuits is based on the phenomenon of the impact of the electric field with conductors, in particular the human body, which is filled with electrolytes and surrounded by a conductive layer of lossy dielectric—the skin. The electronic component that produces the electric field is obviously a capacitor and as with any capacitor each part of the field goes out the covers. This field is called the boundary field. The system of covers in the touch switch is designed so that the field is the greatest and directed to the area available to the user's finger. It can be seen that the capacitor with parallel covers is not a good structure in this case, because the produced boundary field is minimal. The finger located in the boundary electric field introduces a certain capacity into the chip, which is called touch capacitance (CD). The capacity of the switch without the presence of a finger in a field boundary is defined as proper capacitance (CP). The widespread belief that for the correct operation of capacitive circuits the finger must be grounded, is wrong. The presence of the finger is detected by the boundary field, as it can store charge, and this fact does not affect its possible grounding.
Referring first to FIG. 1, an embodiment of a prior art capacitive touch system, e.g., capacitor, is shown. The diameter of the pillow switch for this example is 10 mm, which is the average size of an adult human fingertip. The mass is also on the top side of the plate, whereby the pillow-mass system can be regarded as a capacitor in which a large part of the energy is stored on the surface of the plate. The pad is isolated from the mass with a ring-shaped gap, the width of the gap is an important design parameter. If it is too small, most of the energy of the electric field “escapes” directly to the mass. However, if it is too large, it becomes impossible to control the marginal distribution of the electric field.
For proper operation of the system, an appropriate choice of the current of the current source and operating frequency of the generator is also necessary. By default, the current source is about 14 ρA and the capacitance measurement time for a single switch is 500 ms. From the analysis of the counts plate and differential switch plate it can be concluded that each switch has its proper capacity (CP) of about 15 pF and tactile capacity (CF) of about 0.5 pF. Therefore, pressing the system alters the total capacity of the system by about 3%. The main advantage of the capacitive touch systems over their mechanical counterparts is that they do not wear out during the operation. However, only the progress in recent years in the field of signal processing has greatly reduced the costs and increase their sensitivity and reliability.
Resistance haptics require two electrodes, which require contact (short circuit) with a conductive element (e.g. by touching a finger). They work by reducing the resistance between the electrodes. Such systems are much simpler to build in comparison to capacitive systems. Putting, for example, one or two fingers on the plates to achieve the status of a circuit switched on or closed, and moving away the finger (fingers) switches the device off. Piezoelectric touch system works on the principle of mechanical impact on the piezoceramic elements, usually built directly behind the surface. This solution allows for the construction of tactile interfaces of each type of material. Current solutions allow the construction of such systems in such a way as touching with a force of 1.5 N is sufficient even for rigid materials such as stainless steel.
In the prior art KR 20130091493 (A), a graphene touch panel that includes etched graphene layer combined with an organic insulator is disclosed. The invention particularly relates to a method for manufacturing the touch panel by gluing etched graphene layer (208) using a polymer punch and organic solvent, and imprinting it on the base substrate (202). Glass or plastic selected from polyethylene terephthalate (PET), polyethylene naphthalate (TEN), polyethersulfone (PES), and polycarbonate (PC) are used as such a substrate.
From the KR 20130055111 publication, a graphene touch panel including a layer of graphene (24) on a substrate (10) is also disclosed. The invention particularly relates to a method for the preparation of the graphene layers of the touch panel by forming the starting graphene oxide film (20) on the substrate (10) and its attachment to the substrate by a process of injection of nitrogen gas and carbon dioxide gas into the chamber and then through the laser irradiation of the graphene oxide film a graphene film (24) is obtained.
In addition, touch screen including etched conductive graphene layer, made by laser etching on this screen is known from the CN 103071925 publication. All publications cited above disclose touch screens comprising a layer of graphene on substrates, including glass or plastic, where the graphene layers are formed and fixed in different manners to the surface of the touch panel.
Therefore, the object of this invention is to provide a novel touch switch comprising a layer of graphene polymer based on flexible graphene nanocomposite which allows to increase the functionality of the electronic devices in their excitation and/or transition to sleep mode.